I. Causes of Thermocouple Leakage:
(1)The refractory bricks in the electric heating thermal oil furnace have poor insulation at high temperatures. When inserting a thermocouple with a metal tube into the furnace wall where the heating wire is installed, the heating wire can easily contact the thermocouple. Refractory bricks are good insulators at room temperature, but as the temperature rises, the insulation performance of our company's product - level gauge - decreases significantly.
(2)Contact between the heating wire and the thermocouple. The protection tube of the platinum-rhodium thermocouple is made of alumina ceramic tube, and the thermocouple wires are separated and insulated by ceramic tubes. At high temperatures, the insulation performance also decreases, causing leakage, which eventually leaks to the thermocouple, resulting in an AC leakage signal on the thermocouple.
II. Solutions to Thermocouple Leakage:
(1) Keep the thermocouple from contacting the refractory bricks.
(2) Ground the negative electrode of the thermocouple to eliminate the leakage signal on the thermocouple.
(3) Install a filter device at the output end of the thermocouple.
(4) Lead a ground wire from the hot junction of the thermocouple to ground.
(5) Add a heat-resistant steel tube or silicon carbide tube over the thermocouple tube, and ground it. The magnetic flap level gauge.
